1 /* IEEE754 floating point arithmetic 2 * double precision: common utilities 3 */ 4 /* 5 * MIPS floating point support 6 * Copyright (C) 1994-2000 Algorithmics Ltd. 7 * 8 * ######################################################################## 9 * 10 * This program is free software; you can distribute it and/or modify it 11 * under the terms of the GNU General Public License (Version 2) as 12 * published by the Free Software Foundation. 13 * 14 * This program is distributed in the hope it will be useful, but WITHOUT 15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 * for more details. 18 * 19 * You should have received a copy of the GNU General Public License along 20 * with this program; if not, write to the Free Software Foundation, Inc., 21 * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. 22 * 23 * ######################################################################## 24 * 25 */ 26 27 28 #include "ieee754dp.h" 29 30 ieee754dp ieee754dp_add(ieee754dp x, ieee754dp y) 31 { 32 COMPXDP; 33 COMPYDP; 34 35 EXPLODEXDP; 36 EXPLODEYDP; 37 38 CLEARCX; 39 40 FLUSHXDP; 41 FLUSHYDP; 42 43 switch (CLPAIR(xc, yc)) { 44 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): 45 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN): 46 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): 47 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN): 48 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN): 49 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN): 50 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN): 51 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO): 52 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM): 53 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM): 54 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF): 55 SETCX(IEEE754_INVALID_OPERATION); 56 return ieee754dp_nanxcpt(ieee754dp_indef(), "add", x, y); 57 58 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN): 59 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN): 60 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN): 61 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN): 62 return y; 63 64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN): 65 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO): 66 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM): 67 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM): 68 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF): 69 return x; 70 71 72 /* Infinity handling 73 */ 74 75 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): 76 if (xs == ys) 77 return x; 78 SETCX(IEEE754_INVALID_OPERATION); 79 return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y); 80 81 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): 82 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): 83 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): 84 return y; 85 86 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO): 87 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): 88 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): 89 return x; 90 91 /* Zero handling 92 */ 93 94 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): 95 if (xs == ys) 96 return x; 97 else 98 return ieee754dp_zero(ieee754_csr.rm == 99 IEEE754_RD); 100 101 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): 102 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): 103 return x; 104 105 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): 106 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): 107 return y; 108 109 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): 110 DPDNORMX; 111 112 /* FALL THROUGH */ 113 114 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): 115 DPDNORMY; 116 break; 117 118 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): 119 DPDNORMX; 120 break; 121 122 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): 123 break; 124 } 125 assert(xm & DP_HIDDEN_BIT); 126 assert(ym & DP_HIDDEN_BIT); 127 128 /* provide guard,round and stick bit space */ 129 xm <<= 3; 130 ym <<= 3; 131 132 if (xe > ye) { 133 /* have to shift y fraction right to align 134 */ 135 int s = xe - ye; 136 ym = XDPSRS(ym, s); 137 ye += s; 138 } else if (ye > xe) { 139 /* have to shift x fraction right to align 140 */ 141 int s = ye - xe; 142 xm = XDPSRS(xm, s); 143 xe += s; 144 } 145 assert(xe == ye); 146 assert(xe <= DP_EMAX); 147 148 if (xs == ys) { 149 /* generate 28 bit result of adding two 27 bit numbers 150 * leaving result in xm,xs,xe 151 */ 152 xm = xm + ym; 153 xe = xe; 154 xs = xs; 155 156 if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */ 157 xm = XDPSRS1(xm); 158 xe++; 159 } 160 } else { 161 if (xm >= ym) { 162 xm = xm - ym; 163 xe = xe; 164 xs = xs; 165 } else { 166 xm = ym - xm; 167 xe = xe; 168 xs = ys; 169 } 170 if (xm == 0) 171 return ieee754dp_zero(ieee754_csr.rm == 172 IEEE754_RD); 173 174 /* normalize to rounding precision */ 175 while ((xm >> (DP_MBITS + 3)) == 0) { 176 xm <<= 1; 177 xe--; 178 } 179 180 } 181 DPNORMRET2(xs, xe, xm, "add", x, y); 182 } 183